1. Field of the Invention
This invention relates to a separation plate mounted on the valve body of an automatic transmission (AT) and having a foamed rubber layer formed on both sides or one side of a separation plate body that is a substrate, and a method for producing the same.
2. Description of the Prior Art
A separation plate is mounted on the valve body of an automatic transmission so as to be nipped between halved valve bodies, and this separation plate 1 comprises a steel product-made separation plate body 2 that is a substrate and a foamed rubber layer 3 applied to both sides or one side (both sides in the drawing) thereof as shown in FIG. 8.
This separation plate 1 for automatic transmission has the function as a receiving seat for receiving the spring of an accumulator or the ball of a ball check valve in addition to the sealing function for sealing the halved valve bodies together, and with respect to the part functioning as the receiving seat, the foamed rubber layer 3 is removed in only this part to expose the hard separation plate body 2 as shown in the same figure.
This surface exposed part 2a was formed in the past by covering the whole surface of the separation plate body 2 with the foamed rubber layer 3, and thereafter removing the unnecessary part 3a of the foamed rubber layer 3 by means of water jet or milling. Such a method, however, required much labor and time and higher cost because of the difficulty of uniform removal and the complicated working.
In producing the separation plate 1, the whole surface of a steel plate for forming the separation plate body 2 is covered with the foamed rubber layer 3 to mold a layered product, and the resulting layered product is then punched into a product form by press working. At that time, however, rubber burrs are generated on the circumferential part and hole peripheral part of the separation plate 1 by the press working, and such rubber burrs inconveniently flow into the valve body as foreign matter to cause a trouble in operation of the valve.
One object of this invention is to provide a separation plate relatively easy to produce, advantageous in cost, and free from rubber burs, and a method for producing the same. Another object of this invention is to provide a separation plate capable of exhibiting excellent sealing function and a method for producing the same.
A separation plate according to claim 1 of this invention is a separation plate mounted on the valve body of an automatic transmission and having a foamed rubber layer formed on both sides or one side of a separation plate body, the foamed rubber layer being applied only to the part necessary for sealing by means of dispenser coating or screen coating.
A separation plate according to claim 2 of this invention is a separation plate mounted on the valve body of an automatic transmission and having a foamed rubber layer formed on both sides or one side of a separation plate body, the foamed rubber layer being applied to the separation plate body according to the form of a land part provided on the valve body, and the foamed rubber layer being applied to the separation plate body in a width larger than the width of the land part.
A method for producing a separation plate according to claim 3 of this invention is a method for producing a separation plate mounted on the valve body of an automatic transmission and having a foamed rubber layer formed on both sides or one side of a separation plate body, which comprises applying the foamed rubber layer only to the part necessary for sealing by means of dispenser coating or screen coating.
A method for producing a separation plate according to claim 4 of this invention is a method for producing a separation plate mounted on the valve body of an automatic transmission and having a foamed rubber layer applied to both sides or one side of a separation plate body, which comprises applying the foamed rubber layer to the separation plate body according to the form of a land part provided on the valve body, and applying the foamed rubber layer to the separation plate body in a width larger than the width of the land part.
When the foamed rubber is applied only to the part necessary for sealing the separation plate body by means of dispenser coating or screen coating as in the separation plate or the method for producing the same according to claim 1 or 4 of this invention, the part to be coated with the foamed rubber is limited to only the part necessary for sealing, and the seal unnecessary part including the part forming the receiving seat to a spring or ball is not covered with the foamed rubber from the first of the production.
Since the dispenser coating or screen coating is suitable to perform the coating only to a desired part of a flat surface to be coated, the coating of the foamed rubber is performed after the press working (after the material steel plate is press worked into the product form as separation plate body, the foamed rubber is applied to a prescribed part of the separation plate body), or the coating of the foamed rubber is performed so that the foamed rubber does not extend to the press end surface (press cut surface) [after the foamed rubber is applied only to a prescribed part so as not to extend to the part forming the press end surface (press cut surface) later on the flat surface of the material steel plate, the resulting material steel plate is press worked into the product form as separation plate body], whereby generation of rubber burrs in the press working of the material steel plate can be prevented.
When the foamed rubber layer is applied to the separation plate body according to the form (land form) of the land part provided on the valve body as in the separation plate or the method for producing the same according to claim 2 or 5 of this invention, the part to be coated with the foamed rubber is limited to only the part according to the form of the land or the part necessary for sealing, and the seal unnecessary part including the part forming the receiving seat to the spring or ball is not covered with the foamed rubber from the first of the production. The land part is a protruding contact part or pressing part to the separation plate preliminarily provided on the valve body or a housing thereof.
Since the foamed rubber layer is applied to the separation plate body in a width larger than the width (land width) of the land part in the separation plate and the method for producing the same according to claim 2 or 5, the rubber thickness of the part with which the land part makes contact can be uniformed more. Accordingly, the local concentration of surface pressure can be avoided, and the part not fastened to the valve body (housing) is provided on the outside, whereby the flow of the fastening rubber to the outside can be suppressed, and the breakage, leakage and peeling of the rubber layer can be prevented. Further, the swollen part of rubber in the part not nipped by the valve body (housing) also exhibits the effect of blocking the leak passage, and the sealing performance can be accordingly improved.
According to claim 3 of this invention, the foamed rubber layer has a gently sloped root.